1. Field of the Invention
The present invention relates to a decoding device which decodes a file read from an external recording medium. Examples of the decoding processes are to decompress a compressed music file and decompress compressed image data to reproduce the data.
2. Description of the Related Art
Referring to FIG. 10, a conventional decoding device which executes a decoding process, such as the reproduction of a compressed file, is described. The compressed file is obtained through a USB interface or the like. An external recording medium 1 is detachably provided in a decoding device 7. The decoding device 7 comprises an interface 2, an operation unit 3, a processor 4, a memory 5, and a decoded data output unit 6. The processor 4 comprises a CPU 41 and a ROM 42. The memory 5 comprises a RAM 51. The processor 4 executes the decoding process using the memory 5.
Below is described an operation of the decoding device 7. First, the external recording medium 1 is connected to the decoding device 7, and a “reproduction button” of the operation unit 3 is then pressed by an operator. Responding to the operation of the operation unit 3, the processor 4 analyzes data recorded on the external recording medium 1 via the interface 2 comprising a USB terminal.
In the case where the decoding device 7 is compliant with the reproduction of a recording medium having a plurality of file structures, first, the file structures of the external recording medium 1 are discriminated from one another. After the file structures are thus identified, information of all of files and folders stored in the external recording medium 1 is read therefrom. Based on the read information, the parentage of the respective files and folders, the total number of the files stored in the respective folders and the external recording medium 1, the total number of the folders, and the like are analyzed.
An analysis result thereby obtained is stored in the memory 5 as file analysis information, and a file designated by the operation unit 3 is thereafter read. Then, the read file is decoded by the decoded data output unit 6, so that data, such as music data, is reproduced.
There is a case in which a power supply for the whole decoding device 7 is disconnected after the external recording medium 1 is analyzed by the decoding device 7, or the external recording medium 1 is removed from the decoding device 7 and reconnected thereto after the external recording medium 1 was analyzed as described. In that case, the external recording medium 1 is regarded by the decoding device 7 as an unknown external recording medium which has not been analyzed yet. As a result, a reproduction instruction is given to the external recording medium 1 by the operation unit 3, and the file analysis is repeated. This technology is recited in, for example, the Japanese Patent Documents (2007-178646 and 2007-179632 of the Japanese Patent Applications Laid-Open). However, in the foregoing cases, the decoding device 7 repeats the file analysis to the external recording medium 1 which was already analyzed once, which makes the data reproduction unnecessarily time-consuming.